Luzon refers to the largest and most economically & politically important island in the Philippines and to one of the three island groups in the country, with Visayas and Mindanao being the other two. Luzon as an island group includes the island of Luzon itself, plus the Batanes and Babuyan groups of islands to the north, and the main and outlying islands of Catanduanes, Marinduque, Masbate, Romblon, and Mindoro in the south. The island group of Palawan, which used to be a province belonging to an administrative region of Luzon has been transferred to Region VI in the Visayas in 2005.[1]

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History

Land bridges connecting the islands of the Philippines, including Luzon to the rest of Southeast Asia were thought of to have brought the earliest settlers to the Philippine archipelago dating back to ca.250,000 B.C.E.

During the Philippine-American War, U.S. forces fought Filipino revolutionaries in various parts of Luzon. In 1901, U.S. Brigadier General J. Franklin Bell told the New York Times that "One-sixth of the natives of Luzon have either been killed or have died of the dengue fever in the last two years. The loss of life by killing alone has been great, but I think that not one man has been slain except were his death served the legitimate purposes of war. It has been necessary to adopt what other countries would probably be thought harsh measures, for the Filipino is tricky and crafty and has to be fought in his own way.[2]

On December 8, 1941 (December 7, 1941 east of the International Date Line), Japanese aircraft attacked U.S. bases on Luzon, launching a campaign which would lead to the landing of invasion forces in various parts of the island. The major landings took place at Lingayen Gulf on December 22. In the face of superior Japanese forces, U.S. and Philippine troops began a series of phased withdrawals to the Bataan Peninsula, where they hoped to hold out until relief could be organized from the U.S. and to deny the Japanese use of Manila Bay through control of Corregidor Island at the southern tip of Bataan. The Battle of Bataan would last for several months, but U.S. and Philippine forces were eventually overwhelmed by the Japanese. Japanese forces completed the occupation of Luzon, but were harassed by U.S. and Filipino guerrillas, in many cases fighting in the same areas where Filipino guerrillas had harassed U.S. forces during the Philippine-American War.

Following earlier landings on Leyte and Mindoro Islands, U.S. forces landed on Luzon, at Lingayen Gulf, on January 9, 1945. Driving southward along the same general route the Japanese followed in 1941-42, they advanced on Manila and fought the Japanese in the Battle for the Liberation of Manila from February to March 1945. U.S. forces also landed in several other points on Luzon and conducted operations to rescue prisoners of war at Cabanatuan and Los Baños. In the face of U.S. advances, Japanese forces retreated to the mountains of Luzon and fought a protracted campaign against U.S. forces into the summer of 1945. Luzon and the rest of the Philippines were officially declared liberated on July 5, 1945.

Administrative Divisions

The eight regions are listed below, discussed individually.
Its administrative centers are for formality's sake only, meaning, there is no 'valid' regional administrative center (except in the case of Administrative regions), the power being vested by the provincial governments. The regional centers are only the head tourist offices for the region.

Cagayan Valley (Region II) is located in the northeast portion of the main island and also covers the Batanes and Babuyan islands to the north. The valley is surrounded by the Cordillera Central and Sierra Madre mountain ranges. Running through its center is the country's longest river, Cagayan River. Its provinces are Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. The region's administrative center is Tuguegarao City in Cagayan province.

CALABARZON (Region IV-A), one of the newest regions of the country, was previously a part of Southern Tagalog (Region IV). It is one of the most populated areas of the country. The name of the region is actually an acronym that stands for its provinces, which are Cavite, Laguna, Batangas, Rizal, and Quezon. The Tagalogs are the dominant ethnic group in this region, with Tagalog as the main language. Its recognized regional capital and administrative center is Calamba, in Laguna, however, other government officials also consider Lucena City, in Quezon province as the administrative center

MIMAROPA (Region IV-B), along with CALABARZON is the newest region of the country, and was previously a part of Southern Tagalog (Region IV). It contains most of the islands in the Luzon group. The name of the region is actually an acronym that stands for its provinces, which are Marinduque, Occidental Mindoro, Oriental Mindoro, Romblon, and formerly Palawan, which is now in the Western Visayas region.

Bicol Region (Region V) occupies the Bicol Peninsula at the southeastern end of Luzon island, plus the outlying islands which include the island provinces of Catanduanes and Masbate. The remaining mainland provinces are Albay, Camarines Norte, Camarines Sur, and Sorsogon. The region's administrative center is Legazpi City in Albay. The inhabitants are of Bicolano descent with Bikol as the main language.

National Capital Region (NCR) is a special administrative region that contains the capital of the country, Manila; the country's most populous city, Quezon City; and an additional 15 more cities and municipalities. The region is more popularly known as Metro Manila. It is the only region in the country that has no provinces, and is the most densely populated with over 10 million people living in a 636 km² area.

The main part of the island is roughly rectangular in shape and has the long Bicol Peninsula protruding to the southeast. The northern part of the island contains the largest mountain range in the country, the Cordillera Central. Mount Pulag, the second highest mountain in the country, is located there, rising 2,922 m. To the east of the Cordillera Central is the large Cagayan Valley, which serves as the basin for the Cagayan River, the longest river in the Philippines. To the east of the valley rises the Sierra Madre mountain range, easily the longest range in the country.

The Sierra Madre snakes southwards into the central and southern part of the island. Between it and the Zambales Mountains to the west is the largest plain, the Central Luzon plain. This plain, approximately 11,000 km² in size, is the country's largest producer of rice. Among the rivers irrigating this plain, the longest are Agno to the north, and Pampanga to the south. In the middle of the plain rises the solitary Mount Arayat. To the west, in the Zambales Mountains, rises Mount Pinatubo, made famous because of its enormous 1991 eruption.

The Zambales mountains extends to the sea in the north, forming Lingayen Gulf, home to the Hundred Islands National Park. To the south, the mountains also extend into the sea, forming the Bataan Peninsula, which encloses the Manila Bay. This natural harbor is considered to be one of the best natural ports in Southeast Asia, due to its size and strategic geographical location.

To the southeast of Manila Bay is the largest lake in the country, and also the largest inland lake in Southeast Asia, the Laguna de Bay (Old Spanish, Lake of Bay town). This 949 km² lake is drained by the Pasig River into Manila Bay. Pasig River is one of the most important rivers in the country due to its historical significance and because it runs through the center of Metro Manila.

Located just 20 km southwest of Laguna de Bay is Taal Lake, within the southwestern portion of the island. This caldera of a lake contains the smallest volcano of the country, Taal Volcano, which rises on the island in the center of the lake. The volcano in turn has a lake in its crater. All the surrounding areas of Taal Lake were once part of a massive prehistoric volcano that covered the southern portion of the province of Cavite, Tagaytay City, and the whole of Batangas province.

Off the southwestern portion of Luzon is the island of Mindoro, separated by the Verde Island Passages. The passages connect the South China Sea to the east with the Tayabas Bay. To the south of the bay is the island of Marinduque.

Island group

The island group of Luzon is an arbitrary grouping of islands divided into eight regions, which are further subdivided into 37 provinces, of which only seven are not on Luzon island itself. The island group includes the Batanes and Babuyan islands to the north, and the islands of Catanduanes, Masbate, Marinduque, Romblon, and Mindoro in the south.

Tectonics

Luzon is a mobile belt, or a fast deforming plate boundary zone--- hemmed in between two opposing subduction zones, the west-dipping Philippine Trench - East-Luzon Trough subduction zone, and the east-dipping north-south trending Manila Trench(Hamburger et al., 1982). The Philippine Sea Plate subducts under Luzon on the east (along the Philippine Trench) while the Sunda block (part of the Eurasian plate subducts under Luzon along the Manila Trench at the western part (Rangin, et al., 1999).

The SE-NW trending left-lateral strike-slip Philippine Fault System traverses Luzon, from Quezon province/Bicol to the northwestern part of the island. This fault system takes up part of the motion due to the subducting plates and produces large earthquakes. Southwest of Luzon is a collision zone where the Palawan-Borneo block collides with SW Luzon, producing a highly seismic zone near Mindoro island. SW Luzon is characterized by a highly volcanic zone, called the Macolod Corridor, a region of crustal thinning and spreading.
Using seismic and geodetic data, Luzon has been modeled as a series of six micro blocks or micro plates, all moving and rotating in different directions, with maximum velocities ~100 mm/yr NW with respect to Sundaland/Eurasia (Galgana et al., 2007). This highly deforming, multi-block nature of Luzon is also noted in its Geologic make up, as cited by Pubellier et al.(2004) among others.

Spanish has a history on the island, primarily due to educated illustrados (including José Rizal) as well as authorities of the Spanish Empire. Spanish was the language of Philippine Revolution, and the 1899 Malolos Constitution proclaimed it as the official language. However, its use declined following the American occupation of the Philippines.